Tilt indicating apparatus



M. F. DORN ET AL TILT INDICATING APPARATUS Filed Oct. 27, 1954 April 22,195s .N di

f f atea Tllfl INDICATING APPARATUS Application October 27, 1954, SerialNo. 465,084

10 Claims. (Cl. 33 266) This invention relates to displaceahle apparatusand particularly to the illumination of indicating apparatus. Theinvention applies especially, but not exclusively, to level indicatorssuch as turn-and-bank indicators, inclinometers and the likefor mobilecraft.

It is an object of the present invention to provide improveddisplaceable apparatus.

lt is another object of the invention to provide improved indicatingapparatus which is economical in construction involving few parts andwherein an index body movable along a curved path is indirectlyilluminated,

it is another object of the invention to provide means for indirectlyilluminating an unattached index body displaceable along a curved pathwhereby a luminous simulated index of predetermined configuration,preferably in the general shape of a pointer, is produced withcontrasting background by controlled rellection of the indire-t lightfrom selected portions of the index body.

It is another object of the invention to provide in a level indicator ofthe type having a spherical mass or ball displaceable along an arcuatepath in an arcuate lightconducting tube filled with a light-conductingdamping uid, means for indirectly illuminating selected portions of theball from selected portions of the tube so as to present to the observera predetermined pattern of reected light which remains substantially thesame in size, shape and intensity when the ball occupies dilerentpositions along the arcuate path.

lt is still another object of the invention to provide irnprovedindicating apparatus including common light source means providingindirect illumination not only of an index body movable along an arcuatepath but also of the indicia on an associated light-conducting memberand/ or of an accompanying light-conducting pointer.

The above and other objects and features of the present invention willbecome more apparent hereinafter from a consideration of the detaileddescription which follows taken together with the accompanying drawingwherein one embodiment of the invention is illustrated by way ofexample. In the drawing wherein like reference characters refer to likeelements through the several views,

Fig. l is a front view of an inclinometer-type indicating deviceembodying the present invention with a portion of the cover assemblybroken away to show the entire arcuate ball-carrying tube positioned inthe lighting plate or dial adjacent to the indicia of one scale and toshow an auxiliary pointer cooperating with a second scale;

Fig. 2 is a cross-sectional view of part of the device of Fig. l takenalong the line 2 2;

Fig. 3 is a cross-sectional view of part of the device of Fig. l takenalong the line 3 3 to show the mounting of one lamp and its positionrelative to the lighting plate;

Fig. 4 is a cross-sectional view of the lighting plate taken along theline 4 4 of Fig. l With other parts omitted;

Fig. 5 is a developed cross-sectional view of the lighting plate takenalong the line 5 5 of Fig. l with other parts omitted;

arent O rice Fig. 6a illustrates diagrammatically the index pattern ofreilected light presented to the observer when the ball is simplyilluminated directly by daylight or another ambient source of light;

Fig. 6b illustrates the broken index pattern presented to the observerwhen the ball is indirectly illuminated only by light rays transmittedfrom the two ends of the tube;

Fig. 6c illustrates the composite index pattern presented to theobserver when the ball is indirectly illuminated by light from the endsof the tube and also by light projecting from a narrow uncoated marginalportion of the tube;

Fig. 7a corresponds to Fig. 6c and illustrates the index patternpresented to observer when the arcuate tube is positioned in thelighting plate as shown in Fig. 2;

Fig. 7b illustrates the index pattern presented to the observer if thearcuate tube is not positioned in the lighting plate as deeply as shownin Fig. 2; and

Fig. 7c illustrates the index pattern presented to the observer when thearcuate tube is positioned in the lighting plate more deeply than shownin Fig. 2.

Turning to Figs. 1 and 2 there is illustrated an inclinometer-typelevel-indicating instrument suitable not only for direct illumination bydaylight or other ambient light but also especially adapted for use in adarkened environment requiring so-called night vision and hence frequiring indirect illumination accompanied by a minmum of stray lightand glare. A ilange portion 11 of housing l2 is secured to a flangedbezel portion 13 of a cover member 14 by screws 15. Sandwiched betweenthe opposed ange portions is a sealing gasket 16. Within a recess in thecover member is a rubber gasket 17 surrounding the rim of a transparentwindow or cover glass 18. A beveled surface 19 of the cover memberserves as a frame for window 18.

A support structure is attached to the sides of the housing and includesan annular member 20. Secured to member 20 by screws 21 is a lightingplate or dial plate 22 of light-transmitting plastic material such asmethyl methacrylate, more commonly known as Lucite or Plexiglas Asindicated in Fig. l the lighting plate is of generally semi-circularshape except for the ilattened sides :z b and c d. The lighting plate 22is highly polished on all surfaces and has its front surface 23 and itsperipheral surfaces 24 covered by a thin layer of white paint which inturn is covered by a layer of opaque paint or printers ink, the dialindicia 25 and 26 of upper and lower scales on the front surface beingcut out of the opaque layer to reveal the layer of white paintunderneath. In an alternative construction, the indicia 2S and 26 may becut or engraved in the front surface 23 of the lighting plate and theresulting recesses filled with white paint, the remaining flat surfaceportions of surface 23 being covered with a layer of opaque paint orprinters ink which may be applied by a roller. In either constructionwhen light rays from one or more sources of light about to be describedare transmitted by internal reflection through lighting plate 22, theindicia 25 and 26 are seen as white or colored light against a darkcontrasting background provided by the opaque layer. If desired,selected portions of the back surface 27 of the lighting plate may bepainted White to provide additional reflection and increase theintensity of illumination of the indicia.

The cover member 14 is provided with a pair of threaded apertures 28which are aligned respectively with a pair of apertures 29 in thelighting plate 22. As indicated best in Fig. 3 a pair of conventionallamps 30 and 31 are threaded through the outer or front end of the covermember by means of a screw-driver inserted in a slot 32 provided in theend of each lamp. When each of the lamps is fully inserted, its lament33 is preferably located approximately midway between the outer andinner surfaces of the lighting plate and its-contacts 34 and 35 makeelectrical contact with respective socket contacts 36 and 37 to completea circuit between the lament and energizing meanstnot shown) within thehousing 12.

The lighting plate 22 is provided with a conically shaped aperture 39located midway between the lamps 30 and 31. The conical surface 40preferably has a 45 slope with respect to the inner and outer surfacesof the lighting plate. Located behind aperture 40 is a mechanism 41 forangularly displacing a shaft 42 which in turn dis- -yplaces a pointer43. Pointer 43 may be composed of Lucite or Plexiglas which is highlypolished on all surfaces and is tapered toward its tip end, the bottomor inner surface portion of the tip end preferably being coated with alayer of white paint 44. As shown in Fig. 2 the front edge surfaceportion 4S of the tail end of the pointer is flat and preferably has a45 bevel or slope with respect to the front and back faces of thelighting plate. By this construction some of the light rays emitted fromthe lamps 29 and 30 are transmitted by internal reflection through thelighting plate and are then reflected from the 45 conical surface 40outwardly from the lightingplate into the underside of pointer 43regardless of the angular position which the pointer happens to be in.Such light rays are in turn reected from the 45 tail-end surface 45 andtransmitted by internal reflection to the pointed tip end portion of thepointer so that the tip end portion glows with uniform high intensityfor the different angular positions of the pointer in contrast with thedark background provided by the dial portions which bear the whiteindicia 25 of the upper scale. Secured to the inner side of the covermember by screws 47 is an opaque shield member 48 of semi-circular shapeto mask all but the tip of the pointer from the view of the observer.

An arcuate groove 49 is provided in the lighting plate. Groove 49 isdefined by the dat surface 50 parallel to the front and back faces ofthe lighting plate, by the upper Wall surface e-f-g-h--i-j-k-l and bythe lower wall surface m1-n1-o1m2-n2-o2. Except as hereinafter noted,the three surfaces defining groove 49 are coated by a layer of Whitepaint which in turn is covered by a layer of opaque paint. Positioned ingroove 49 is an arcuate hollow tube 52 of light-conducting ortransparent material such as Pyrex glass. In order to absorb shock orvibration a rubber strip 53 is interposed between the tube and surfaceand a rubber strip 54 is interposed between the tube and surfaceml-n-l-ormz--nz-og. The tube 52 is releasably secured in groove 49 bysuitable means such as clamps 55 which have one end fastened to thelighting plate by means such as screws 55.

A spherical solid ball 56 of highly polished tungsten carbide isconfined inside tube 52 with a small clearance between the inner Wallsof the tube so that when the housing, lighting plate and tube are tiltedto the left or right of dead center the ball correspondingly rolls alongits arcuate path to the left or right of the zero position to an extentdepending upon the direction and degree of tilt. Ball 56 cooperates withthe indicia 26 of the lower scale to give an indication of the directionand degree of tilt.

Tube 52 is preferably filled with a damping fluid such as carbontetrachloride or water, although the fluid may be omitted if desired.The ends of tube 52 are sealed off by portions 57 and 58.

When lamps 30 and 31 are not energized and ball 56 is illuminateddirectly by daylight or other ambient light, the pattern of reflectedlight from the ball which the observer may see is indicateddiagrammatically in Fig. 6a, the central portion serving as an indexmark for the ball so that the position of the latter may be ascertained.Due to the presence of the tube and damping huid the prolile of thespherical ball appears generally elliptical in shape. Means willvnow bedescribed for indirectly illuinitiating ball 56 from lamps 30 andl'sovas to obtain a pattern of reflected light from 'the ball whichsimulates a pointer thereby giving an accurate reading and which remainssubstantially the same in size, shape and intensity when the balloccupies different positions along its arcuate path. l

In Fig. 5 there is shown a developed section of lighting plate 22 takenalong the arcuate line 5--5 of Fig. 1. As indicated in Fig. 5 thesurface e--f-g-h-i--j-k--l defining the upper boundary of arcuate groove49 has portions e-,f--j and g-h-k-l covered with an opaque layer, whileportions f--p-i-r and q-g-s--k remain uncoated and serve in effect aswindows 60 and 61, respectively, to permit some of the light raystransmitted through the lighting plate to escape from the plate andenter the adjoining end portions 63 and 64 of the arcuate tube 52. Theend portions 63 and 64 are coated on the outside with a layer of whitepaint which extends around the circumference of the tube forapproximately 270, the remaining 90 which faces a respective one of thewindows 60 and 61 being uncoated so as to receive the light rays fromthe lighting plate.

By this construction the light rays which enter the left-hand end of thetube from lamp 30 are transmitted by internal reflection through thedamping fluid and along the tube until they strike the left-hand portionof ball S6. Similarly, the light rays which enter the right-hand end ofthe tube from lamp 31 are transmitted along the tube until they strikethe right-hand portion of the ball. The resulting pattern of reflectedlight presented to the observer is indicated diagrammatically in Fig.6b, the lefthand strip" of light being derived from lamp 30 and theright-hand strip of light being derived from lamp 31. However, thesestrips are separated by a relatively wide dark area which makes accuratereadings diticult, since the observer is required to estimate thegeometrical center between the strips of light. In accordance withanother feature of the invention means will now be described for closingor filling-in the gap at the outer ends of the strips so as to simulatean inverted U-shaped or V-shaped pointer which facilitates accuratereadings by the observer.

Instead of covering the entire portion p-q-r--s ofthe upper wall withopaque paint only portion t--u--rv-s is covered with opaque paint and anarrow marginal portion p-q-t-u is left uncoated so as to permit some ofthe light rays transmitted through the lighting plate from lamps 30 and31 to escape and enter an adjoining marginal portion of the arcuate tube52. There is thus produced continuously along the tube a narrowreservoir of light of substantially uniform intensity which serves tofill-in the gap in the pattern of light reected from the ball so that,as indicated diagrammatically in Fig. 6c, there results a compositepattern of light in the general form of an inverted U-shaped or V-shapedpointer presented against a contrasting dark background provided by theremaining non-rellecting portions of the ball, the size, shape andintensity of the pattern remaining substantially the same regardless ofthe position which the ball assumes along its arcuate path. lf desired,the lighting plate or at least the portion which includes the upper walle-h--i-l may be replaced by asolid curved tube of light-conductingmaterial such as Lucite supplied from one or both o f the lamps andhaving a convex surface positioned adjacent to arcuate tube S2 andcovered with opaque paint to provide an uncoated marginal strip andpreferably also two end windows, which would be similar to what isprovided on surface e-h-i--l as shown in Fig. 5.

The pointer 43 and upper scale 25 may be used as a Vernier to give amore sensitive indication of small angles of tilt so as to supplementthe indication provided by ball 56 and lower scale 26, in which eventthe mechanism' 41 for actuating pointer 43 may be adapted to senseindependently the gravity forces or other condition to which ball S6responds. If desired, mechanism 41 may be adapted to sense a differentcondition than ball 56 and the upper scale 25 accordingly calibrated-inunits of such condition. Mechanism 41 may include a bellows arrangementor a gyroscope for example.

Various changes may be made in the shape, size or design of the partsand in the configuration or dimensions of the luminous pattern presentedby the ball to the observer. For example, if groove 49 is cut lessdeeply into the lighting plate than illustrated in Fig. 2 so that tube52 and ball 56 are located less deeply in the lighting plate, then thelegs or sides of the inverted U-shaped or V-shaped pointer will appearshorter and will be spaced farther apart as represented diagrammaticallyin Fig. 7b. deeper so that tube 52 and ball 56 are positioned deeper inthe lighting plate, then the legs or sides of the simulated pointer willappear longer and will be spaced closer together as indicated in Fig.7c. Fig. 7a corresponds to Fig. 6c and represents diagrammatically thesimulated pointer which may be obtained when tube 52 and ball 56 areinserted in the lighting plate to the extent indicated in Fig. 2. Incertain applications it may prove desirable that the ball 56 of solidmaterial be replaced by a displaceable body or mass of a differentcharacter, for example an air bubble formed within a suitable liquid intube 52. Also, colored, light filters may be positioned between the lampbulbs and tube 52 or the indicia. Furthermore, in certain applicationsit may be sufficient to provide a single indicium or reference mark atthe zero mark of scales or 26 rather than a series of graduationsforming a scale. Also, indicia 25 and 26 could be provided on one or twoseparate light-conducting plates which are clamped into optical contactwith an uncoated outer surface of lighting plate 22, or instead indicia25 and 26 could be painted with radium paint or the like on separateopaque dials. Moreover, if simple incandescent lighting is not desired,luminescent material and other forms of radiant energy can be utilizedin conjunction with a ball sensitive thereto to yield the simulatedindex pattern desired.

Although one specific embodiment of the invention has been illustratedand described in detail by way of example, it is to be expresslyunderstood that the invention is not limited thereto. Variousmodifications may be made Without departing from the spirit and scope ofthe appended claims as will now be apparent to those skilled in the art.

We claim:

1. In indicating apparatus, a hollow curved light conducting tube, alight-reflecting ball confined within said tube and displaceable alongits curved interior in response to tilting of the tube, a lightconducting member having a curved groove in which said tube is located,

said member having an arcuate light emitting portion along a curved sideof said tube, and means for directing light through said light emittingportion into said tube to illuminate said ball.

2. In indicating apparatus, a hollow arcuate tube of light-conductingmaterial, a quantity of fluid disposed within said tube, alight-reflecting ball confined within said tube and adapted, upontilting of the tube, to be displaced through the fluid along an arcuatepath defined by the interior of said tube to an extent depending uponthe degree of tilt of the tube, and means for producing a simulatedpointer of light reflected from said ball, said means including meansfor projecting light rays into both ends of said tube for transmissionby internal reflection along said tube and by refraction through saidliquid to reflect from opposite surface portions of said ball facing theobserver.

3. In indicating apparatus, a hollow curved lightconducting tube, alight-reflecting ball confined within said tube for displacement along acurved path therein Similarly, if groove 49 is cut in response totilting of the tube, and a light-conducting member having a curvedgroove in which said tube is located, said member having alight-emitting portion adjacent each end of said tube so that light rayspass from said portions into respective end portions of said tube fortransmission inwardly along the tube toward said ball.

4. In indicating apparatus, a hollow arcuate lightconducting tube, alight-reflecting ball confined within said tube for displacement alongan arcuate path therein in response to tilting of the tube, light sourcemeans, and a light-transmitting member having a reference indiciumthereon adapted for illumination by light rays transmitted through saidmember from said source means and having an arcuate groove in which saidtube is locoated, the convex wall of said member which defines part ofsaid groove having a light-emitting portion adjacent each end of saidtube so that other light rays transmitted through said member from s-aidsource means pass from said light-emitting portions into respective endportions of said tube for transmission inwardly along the tube towardsaid ball.

5. In indicating apparatus, a hollow arcuate lightconducting tube, alight-reflecting ball confined within said tube for displacement alongan arcuate path therein in response to tilting of the tube, light sourcemeans, a light-transmitting member having indicia thereon adapted forillumination by a first group of light rays transmitted through saidmember from said source means and having an arcuate groove in which saidtube is positioned, said tube being positioned in close proximity to theconvex wall of said member which constitutes the convex boundary of saidgroove, and a layer of opaque material overlying said convex wall exceptfor three selected portions of said wall, one of said selected portionsbeing located adjacent to one end of said tube so that a second group oflight rays transmitted through said member from said source means escapefrom said one portion and pass into said one end of the tube fortransmission along the tube to reflect from a first surface portion ofsaid ball, a second one of said selected portions being located adjacentto the other end of said tube so that a third group of light raystransmitted through said member from said source means escape throughsaid second portion and pass into said other end of the tube fortransmission along the tube to reflect from a second surface portion ofsaid ball, the third one of said selected portions comprising arelatively narrow marginal portion extending along the length of theconvex wall to interconnect said first and second portions so that afourth group of light rays transmitted through said member from saidsource means escape through said marginal portion and pass into theimmedi- -ate concave portion of said tube to reflect from a thirdsurface portion of said ball, whereby a substantially uniform compositepattern of light reflected from said ball is presented to the observerfor different positions of said ball along said arcuate path.

6. Apparatus according to claim 5 wherein said pattern of reflectedlight has the configuration of an inverted U-shaped or V-shaped pointer.

7. Apparatus according to claim 5 wherein said light source meanscomprises a pair of lamps disposed in said light-transmitting member. A

8. Apparatus according to claim 5 wherein a quantity of light-conductingfluid is confined within said tube for damping said ball.

9. Apparatus according to claim 5 wherein said indicia includes a firstseries of graduations with which said ball cooperates and a secondseries of graduations spaced from said first series, and wherein thereis provided a light-conducting pointer member which cooperates with saidsecond series of graduations and which is adapted to receive a fifthgroup of light rays trans- 'Z mitted through said light-transmittingmember from References Cited in the le of this patent said light sourcemeans.

10. Apparatus according to claim 9 wherein said lightv UNITED .STATESPATENTS transmitting member has a conically shaped aperture 23211152'RYlSkY NOV 12, 1940 which receives said fifth group of light rays andreects 5 2,551,333 l ROSSIS May 1, 1951 sald last-mentioned rays lnto atall-end portion of said FOREIGN PATENTS pointer member for transmissionthrough said pointer Y member to the tip-end portion thereof. 685,707Great Britain Ian. 7, 1953

